This invention relates to a color image copier with a simple structure capable of producing copies of improved color quality.
As disclosed, for example, in Japanese Patent Publication Tokkai 55-162174, a prior art copier of a color image typically exposes a color original sequentially to beams of light with different chromatographic radiation characteristics (such as red, green and blue), takes the reflected light into a CCD sensor by using a lens and mirrors, and obtains image data individually corresponding to these colors by sequentially taking them out in synchronism with the timing of light emission. Yellow, magenta, cyanic and black color data are created from these image data through a color conversion process and a color image is obtained by transferring color ink particles onto a sheet of printing paper by a thermal transfer recording method.
Color image copiers based on this general principle are inevitably complicated in structure, large in size and costly because there must be provided a red light source, a green light source, a blue light source, a control unit for controlling the timing of color light emission, a CCD image sensor, a control unit for controlling the charge timing, a color conversion processor, a thermal transfer recorder, yellow, magenta, cyanic and black ink ribbons, etc.
A prior art light source for a color image copier of analog image reading type is described next by way of FIG. 9 for the purpose of reference. In FIG. 9, numeral 21 indicates a light source such as a fluorescent lamp surrounded by a screen 22 for screening the light emitted from this source 21 to limit its optical path and a unistructurally formed cylindrical R, G and B rotary filter 23, and numeral 24 indicates a photosensor for detecting the revolution of the cylindrical filter 23, for example, by detecting a slit provided at one end of the filter 23. With a light source thus formed, the lamp 21 is lit up and the filter 23 begins to rotate at the beginning of a copying operation. The light from the source 21 is then passed through the R part of the filter 23R first and the reflected R beam from the original 1 is projected onto a film through the lens 3. Next, the light from the source 21 is passed through the G part of the filter 23G and the reflected G beam from the original 1 is projected onto the film. Then, the light from the source 21 is passed through the B part of the filter 23B and the B beam from the original is similarly projected onto the film. When the filter 23 completes one revolution and the exposure of the original 1 with R, G and B beams is completed, the photosensor 24 detects the end of a cycle of operation and a pulse motor is started in synchronism with this detection to transport the next original to be copied. The drum (not shown in FIG. 9 but reference may be made to FIG. 1) of the copier is also rotated by a predetermined angle and the copier starts the next cycle of copying operation.
Japanese Patent Publication Tokkai 55-162174, on the other hand, describes a digital color copier using a CCD image sensor to sequentially receive R, G and B beams of light with different chromatographic characteristics. With prior art copiers of the types described above, copying can be effected at an improved rate but editing operations such as image enlargements and reductions cannot be achieved. With conventional digital color copiers, furthermore, not only an image sensor but also a device for controlling the timing of emission of light in different colors, a color conversion device, etc. are required and the copier becomes complicated, large and more costly. Moreover, light-emitting units of the conventional type described above are not efficient because light is projected directly onto the original and hence tends to disperse. The present invention is also addressed to such drawbacks of prior art color copiers.